Category: Obsessive Compulsive and Related Disorders

Symposium

IQ in OCD: A Meta-Analysis of a 120-Year-Old Myth

Saturday, November 18
8:30 AM - 10:00 AM
Location: Sapphire Ballroom A, Level 4, Sapphire Level

Keywords: OCD (Obsessive Compulsive Disorder)
Presentation Type: Symposium

Background: Obsessive compulsive disorder (OCD) is associated with a moderate degree of underperformance on cognitive tests, including deficient processing speed. However, despite little research focusing on Intelligence Quotient (IQ) in OCD, it has long been speculated that the disorder is associated with elevated intellectual capacity, with some accounts dating to 1903. The present meta-analytic study was therefore conducted to quantitatively summarize the literature on IQ in OCD systematically.


Method: We identified 98 studies containing IQ data among individuals with OCD and comparison groups, and computed 108 effect sizes for Verbal IQ (VIQ), Performance IQ (PIQ), and Full Scale IQ (FSIQ).


Results: Across studies, small effect sizes were found for FSIQ (Hedges’ g = .35) and VIQ (g = .19), and a medium effect size for PIQ (g = .58), exemplifying reduced IQ in OCD. However, mean IQ scores across OCD samples were in the normative range (unweighted mean VIQ=110.7; PIQ=106.2; FSIQ=109.1). Moderator analyses demonstrated that later age of onset and increased OCD symptom severity were correlated with lower IQ in OCD samples.


Conclusion: We conclude that, although lower than controls, OCD is associated with normative VIQ and FSIQ, and normative but relatively lowered PIQ. These results, together with results from recent studies, suggest that reduced processing speed may underlie the significant PIQ-VIQ discrepancy in OCD. Notably, this discrepancy was preciously documented in depressed patients. These results will be discussed in light of findings from the extensive body of neuropsychological literature in OCD, and particularly, the putative impact of reduced processing speed in this population. In light of our results we recommend that clinicians and researchers utilize verbal IQ tests to estimate FSIQ, thus bypassing the effects of slowness, facilitating a more precise estimation of FSIQ. Direction for future research will be offered. 

Amitai Abramovitch

Assistant Professor
Texas State University

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